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+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2014 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu build linux-modules)
+ #:use-module (guix elf)
+ #:use-module (rnrs io ports)
+ #:use-module (rnrs bytevectors)
+ #:use-module (srfi srfi-1)
+ #:use-module (srfi srfi-26)
+ #:use-module (ice-9 vlist)
+ #:use-module (ice-9 match)
+ #:export (dot-ko
+ ensure-dot-ko
+ module-dependencies
+ recursive-module-dependencies
+ modules-loaded
+ module-loaded?
+ load-linux-module*
+
+ current-module-debugging-port))
+
+;;; Commentary:
+;;;
+;;; Tools to deal with Linux kernel modules.
+;;;
+;;; Code:
+
+(define current-module-debugging-port
+ (make-parameter (%make-void-port "w")))
+
+(define (section-contents elf section)
+ "Return the contents of SECTION in ELF as a bytevector."
+ (let* ((modinfo (elf-section-by-name elf ".modinfo"))
+ (contents (make-bytevector (elf-section-size modinfo))))
+ (bytevector-copy! (elf-bytes elf) (elf-section-offset modinfo)
+ contents 0
+ (elf-section-size modinfo))
+ contents))
+
+(define %not-nul
+ (char-set-complement (char-set #\nul)))
+
+(define (nul-separated-string->list str)
+ "Split STR at occurrences of the NUL character and return the resulting
+string list."
+ (string-tokenize str %not-nul))
+
+(define (key=value->pair str)
+ "Assuming STR has the form \"KEY=VALUE\", return a pair like (KEY
+. \"VALUE\")."
+ (let ((= (string-index str #\=)))
+ (cons (string->symbol (string-take str =))
+ (string-drop str (+ 1 =)))))
+
+(define (modinfo-section-contents file)
+ "Return the contents of the '.modinfo' section of FILE as a list of
+key/value pairs.."
+ (let* ((bv (call-with-input-file file get-bytevector-all))
+ (elf (parse-elf bv))
+ (modinfo (section-contents elf ".modinfo")))
+ (map key=value->pair
+ (nul-separated-string->list (utf8->string modinfo)))))
+
+(define %not-comma
+ (char-set-complement (char-set #\,)))
+
+(define (module-dependencies file)
+ "Return the list of modules that FILE depends on. The returned list
+contains module names, not actual file names."
+ (let ((info (modinfo-section-contents file)))
+ (match (assq 'depends info)
+ (('depends . what)
+ (string-tokenize what %not-comma)))))
+
+(define dot-ko
+ (cut string-append <> ".ko"))
+
+(define (ensure-dot-ko name)
+ "Return NAME with a '.ko' prefix appended, unless it already has it."
+ (if (string-suffix? ".ko" name)
+ name
+ (dot-ko name)))
+
+(define* (recursive-module-dependencies files
+ #:key (lookup-module dot-ko))
+ "Return the topologically-sorted list of file names of the modules depended
+on by FILES, recursively. File names of modules are determined by applying
+LOOKUP-MODULE to the module name."
+ (let loop ((files files)
+ (result '())
+ (visited vlist-null))
+ (match files
+ (()
+ (delete-duplicates (reverse result)))
+ ((head . tail)
+ (let* ((visited? (vhash-assoc head visited))
+ (deps (if visited?
+ '()
+ (map lookup-module (module-dependencies head))))
+ (visited (if visited?
+ visited
+ (vhash-cons head #t visited))))
+ (loop (append deps tail)
+ (append result deps) visited))))))
+
+(define %not-newline
+ (char-set-complement (char-set #\newline)))
+
+(define (modules-loaded)
+ "Return the list of names of currently loaded Linux modules."
+ (let* ((contents (call-with-input-file "/proc/modules"
+ get-string-all))
+ (lines (string-tokenize contents %not-newline)))
+ (match (map string-tokenize lines)
+ (((modules . _) ...)
+ modules))))
+
+(define (module-loaded? module)
+ "Return #t if MODULE is already loaded. MODULE must be a Linux module name,
+not a file name."
+ (member module (modules-loaded)))
+
+(define* (load-linux-module* file
+ #:key
+ (recursive? #t)
+ (lookup-module dot-ko))
+ "Load Linux module from FILE, the name of a `.ko' file. When RECURSIVE? is
+true, load its dependencies first (à la 'modprobe'.) The actual files
+containing modules depended on are obtained by calling LOOKUP-MODULE with the
+module name."
+ (define (slurp module)
+ ;; TODO: Use 'mmap' to reduce memory usage.
+ (call-with-input-file file get-bytevector-all))
+
+ (when recursive?
+ (for-each (cut load-linux-module* <> #:lookup-module lookup-module)
+ (map lookup-module (module-dependencies file))))
+
+ (format (current-module-debugging-port)
+ "loading Linux module from '~a'...~%" file)
+
+ (catch 'system-error
+ (lambda ()
+ (load-linux-module (slurp file)))
+ (lambda args
+ ;; If this module was already loaded and we're in modprobe style, ignore
+ ;; the error.
+ (unless (and recursive? (= EEXIST (system-error-errno args)))
+ (apply throw args)))))
+
+;;; linux-modules.scm ends here